docs: def hessian(self):
          """
          :return: Hessian filled with the symbolic expressions for all the
              second order partial derivatives. Partial derivatives are taken with
              respect to the Parameter's, not the independent Variable's.
          """
          return [[[sympy.diff(partial_dv, param) for param in self.params]
                   for partial_dv in comp] for comp in self.jacobian]